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Deadly Legionnaires’ disease outbreak in Michigan highlights surveillance issues

A recent outbreak of Legionnaires’ disease in Genesee County, Michigan, underscored surveillance issues surrounding the sometimes deadly lung infection, according to experts.

The outbreak — involving both area health care facilities and the community — is thought to have been caused by municipal water originating from the Flint River, which also was shown to have carried high levels of lead into the homes of area residents. The outbreak infected 87 people between 2014 and 2015, killing nine.

“The United States has lagged far behind the rest of the world in having some kind of standard or requirement for addressing Legionella in building water systems,” Janet E. Stout, PhD, president of Special Pathogens Laboratory in Pittsburgh, told Infectious Disease News.

Janet E. Stout

Research by Stout and others has shown the potentially lifesaving benefits of protecting against outbreaks of Legionnaires’ disease by proactively testing water for Legionella, an approach she has been recommending for more than 30 years.

However, national guidelines regarding Legionella are generally reactive, according to Stout.

“The increase in chance of death happens when there’s a delay in diagnosis and a delay in initiating appropriate therapy,” she said.

The benefits of proactive testing

Stout and colleagues showed in a 1982 study that during an outbreak of Legionnaires’ disease, Legionella was more widely distributed at a Veterans Affairs hospital in Pittsburgh than previously believed. The hospital’s water distribution system was identified as the reservoir for the pathogen.

In a 2005 study, Stout and colleagues demonstrated that guidelines favoring a proactive approach significantly decreased the number of nosocomial Legionnaires’ disease cases in Allegheny County, Pennsylvania, even as there was an increase in community-acquired cases in the area. The county recommended routine testing of the hospital water distribution systems even in the absence of reported cases — a departure from national guidelines.

“The results showed that it was highly effective in reducing hospital-acquired Legionnaires’ disease,” Stout said. “And the reason it was effective is that people tested the water. If they found Legionella in the water, then they disinfected the water system and cases stopped.”

Testing to discover whether or not the water supply contains the bacteria is a “logical” step hospitals can take to protect patients, Stout said.

“If Legionella is present in that water system, then they can protect their patients by disinfecting the water,” she said. “The physicians can protect their patients by being aware that Legionella is a potential cause for pneumonia in their hospitalized patients and then select the right antibiotic.”

Flint outbreak follows switch to river water source

In April 2014, the city of Flint, Michigan, switched its primary water source from the Detroit water system to the Flint River. The switch was to last 2 years while construction of a pipeline from Lake Huron was completed. However, amid an outcry over the levels of lead in the water, Flint was reconnected to the Detroit water system on Oct. 15, 2015.

Two outbreaks of Legionnaires’ disease were detected in Genesee County during the time Flint was getting its water from the river, according to the Michigan Department of Health and Human Services (MDHHS). The first, between June 2014 and March 2015, included 45 confirmed cases, with five associated fatalities. Between May and October 2015, there were 42 confirmed cases and four deaths. The average number of Legionnaires’ disease cases reported in Genesee County over the previous 4 years was between six and 13.

According to the MDHHS, 36% of the patients in the outbreaks used Flint city water in their homes, and 48% had stayed overnight in an area hospital in the 2 weeks before the onset of their symptoms.

During the initial increase between June 2014 and March 2015, more than half of cases had contact with McLaren Medical Center within 2 weeks of symptom onset. McLaren, where Stout has been consulting since August 2015 after working with the county health department, gets its water from the City of Flint. She said the lessons learned from the outbreak are clear.

“Our proactive message,” she said, “is seek Legionella out and you will protect your patients. ... Health care facilities should be testing for Legionella, especially in Genesee County.”